YouhaveanExchangeServer2010organization.UsersonthenetworkuseHTTPStoconnecttoOutlookWebApp（OWA）.TheClientAccessserverusesacertificateissuedbyaninternalcertificationauthority（CA）.Youplantodeployane-mailencryptionsolutionforallusers.Youneedtoensurethatuserscansendandreceiveencryptede-mailmessagesbyusingS/MIMEfromOWA.Whatshouldyoudo？（）

A.Issueacertificatetoeachuser

B.InstructallOWAuserstoimportarootCAcertificate

C.ModifytheauthenticationsettingsoftheOWAvirtualdirectory

D.ConfiguretheClientAccessServertouseacertificateissuedbyathird-partyCA